Asymptomatic bacteriuria (ASB) is specific bacterial growth of ≥105 CFU/mL in one and two consecutive midstream urine samples for men and women, respectively >18 years. This definition applies to individuals with no clinical symptoms.
- Premenopausal females: 1–6%
- Pregnancy: 2–10%
- Older females and males: 4–19%
- ~22% of women >90 years old (1)
- Institutionalized older population: 15–50%
- Variable; increases with age, female gender, sexual activity, neurogenic bladder, and presence of genitourinary (GU) abnormalities
- Pregnancy: 2–10%
- Short- and long-term indwelling catheter 9–23% and 100%, respectively
- Long-term care residents in women 25–50% and men 15–40%
Etiology and Pathophysiology
- Pathophysiology: Most cases are secondary to the ascension of bacteria from the urethra to bladder.
- Microbiology is similar to that of other urinary tract infections (UTI), with bacteria originating from the periurethral area, vagina, or gut.
- Organisms are less virulent in ASB than those causing UTI.
- The most common organism is Escherichia coli. Other common organisms are Klebsiella pneumoniae, Enterobacter, Proteus mirabilis, Staphylococcus aureus, group B Streptococcus (GBS), and Enterococcus.
Genetic variations that reduce toll-like receptor-4 (TLR4) function have been associated with ASB by lowering innate immune response and delaying bacterial clearance.
- Older age
- Female gender
- Sexual activity, use of diaphragm with spermicide
- GU abnormalities: neurogenic bladder, urinary retention, urinary catheter use (indwelling, intermittent, or condom catheter), or pathologic urinary fistulas
- Institutionalized elderly population
- Diabetes mellitus
- Immunocompromised status
- Spinal cord injuries or functional impairment
Commonly Associated Conditions
Depends on the risk factors
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